The BOSU? Ballast? Ball is like no other ball in the gym. This ball has a six-sided surface design for proper alignment and positioning. It also has 2.5 lbs. of multi-dimensional load (ballast) which keeps it from wandering during your workout. The BOSU? Ballast? Ball provides a fun, visual effect and audible feedback during lifting, shifting and shaking exercises. With the BOSU? Ballast? Ball, individuals can perform exercise progressions and dynamic drills that are not possible on a regular exercise ball. Use it like an exercise ball, slam ball, or multidimensional load.